There are many occasions when it is necessary to machine the surface of a bore. Conventionally, where the bore has a constant diameter along its length, a cutting tool is fixedly mounted on a tool carrier and is moved along the bore while the carrier is rotated at a constant angular velocity about a machining axis which is coincident with the longitudinal axis of the bore. The cutting tool, thus, machines around a machining circle of constant diameter. This procedure has the disadvantage that it is not possible to make a fine adjustment of the diameter of the machining circle without remounting the tool on its carrier.
It is conventional, where the bore varies in diameter, ie is profiled, to vary the diameter of the machining circle, as the bore is machined. This is achieved by providing a transverse slideway on the tool carrier and mounting the tool on this slideway. A mechanism extends through the tool carrier, and a tool holder on which the tool carrier is mounted, to a thrust washer or the like which can be moved, eg by a ball screw, to move the tool inwardly or outwardly along the slideway so that the tool moves transversely relative to the tool carrier. This arrangement can also, in principle, be used for making fine adjustments when machining bores of constant diameter. However, not only is this arrangement relatively complex but it also has the disadvantage that the slideway may become clogged with swarf.